Electron beam exposure system method and apparatus

Abstract

An electron beam exposure system and method for use in the process of fabricating microminiature devices at high speeds. The high-speed operation is achieved with a computer providing programmed commands specifying a particular pattern to be scanned. A processor, responsive to programmed data, generates scan data a line at a time and loads a line generator. The line generator steps to each exposure location in a line to provide control signals for controlling the position of the electron beam. The starting and end positions of scan lines in both the X and Y directions may be arbitrarily selected thereby eliminating the need for scanning areas not intended to be processed.

What is claimed is: 
     
       1. An apparatus for controlling an exposing beam to selectively scan a pattern on a work piece comprising, computer apparatus for supplying digital information records specifying the pattern to be scanned,   processor apparatus, connected to receive the information records from said computer apparatus, for converting the information records to line scan information,   line generator apparatus, connected to receive the line scan information from said processor apparatus, for providing beam position signals to scan the exposing beam on the work piece at locations determined by the scan information.   
     
     
       2. The apparatus of claim 1 including, X and Y deflection means responsive to X and Y axis analog signals, respectively, for controlling the X and Y axis deflection of the exposing beam, respectively,   X and Y axis digital-to-analog converters connected to provide said X and Y axis analog signals, respectively, in response to X and Y axis coordinates determined by the beam position signals.   
     
     
       3. The apparatus of claim 1 including a movable table, carrying said work piece, for moving the work piece relative to the scan field of the exposing beam and including drive means for moving said table to a commanded position in response to commands from said computer apparatus. 
     
     
       4. The apparatus of claim 3 including a position measurement unit for measuring the actual position of said table and work piece, including means for providing correction signals as a function of the difference between the commanded position and the actual position of said table, and including means for summing said correction signals with said analog signals whereby the position of said exposing beam is accurately maintained relative to the actual position of said work piece. 
     
     
       5. The apparatus of claim 4 wherein said measurement unit is an interferometer providing digital actual position signals, wherein said computer apparatus supplies digital commanded position signals, and where said apparatus includes a digital subtractor means for forming digital error signals as the difference between said digital actual position signals and said digital commanded position signals and said apparatus includes digital-to-analog converter means for converting said digital error signals to said correction signals. 
     
     
       6. The apparatus of claim 5 including means for providing a stop scan signal when said error signals exceed predetermined magnitudes and including means for inhibiting further scanning during the presence of said stop scan signals. 
     
     
       7. The apparatus of claim 5 including means for providing drive signals to said drive means with magnitudes determined by the magnitudes of said error signals. 
     
     
       8. The apparatus of claim 1 wherein said line generator apparatus includes, X and Y beam position counters for storing X and Y axis coordinates, respectively, for controlling the X and Y axis positions of the exposing beam, respectively,   length counter means for storing a length count representing the number of scan locations in a predetermined direction of scan,   control means including scan axis store means for specifying said X axis or said Y axis as said predetermined direction of scan, said control means including clock means for clocking said length counter means to decrement said length counter and for clocking the one of said beam position counters corresponding to said predetermined direction of scan, said control means including direction store means for specifying a positive or negative direction of scan and responsively controlling the incrementing or decrementing, respectively of said one of said beam position counters by said clock means.   
     
     
       9. The apparatus of claim 8 including sequencer means for loading said position counters, said length counter, said scan axis store means and said direction store means in response to line scan information from said processor apparatus. 
     
     
       10. The apparatus of claim 8 including zero detection means, connected to said length counter means, for detecting when said length counter has been decremented to zero to indicate the end of a line scan and including means to reload said counters and said store means in response to said zero detection to commence a new line scan whereby said exposing beam is scanned to expose said pattern a line at a time. 
     
     
       11. The apparatus of claim 1 wherein said processor apparatus is controlled to provide said line scan information as equal length lines starting at the same coordinate whereby rectangular shapes are scanned. 
     
     
       12. The apparatus of claim 1 wherein said processor apparatus is controlled to provide said line scan information as unequal length lines starting at different coordinates whereby special non-rectangular shapes are scanned. 
     
     
       13. An apparatus for controlling the scanning of a pattern on a work piece comprising, electron beam column apparatus including an electron source providing an electron exposing beam, a deflection unit responsive to deflection signals for selectively deflecting the electron beam over a scan field on a work piece, a work chamber containing the work piece, a table movable relative to the scan field for positioning the work piece and table at a commanded position, a position measurement unit for measuring the actual position of the work piece,   computer apparatus for supplying digital information records specifying the pattern to be scanned and digital command for specifying the commanded position of the work piece and table,   drive means, connected to receive the digital command from said computer apparatus, forming drive signals for positioning the table and work piece at the commanded position,   processor apparatus, connected to receive the information records from said computer apparatus, for converting the information records to line scan information,   line generator apparatus, connected to receive the line scan information from said processor apparatus, for providing beam coordinate signals,   converter means for converting the coordinate signals to deflection signals to scan the exposing beam on the work piece at locations determined by the scan information.   
     
     
       14. The apparatus of claim 13 including means for providing correction signals as a function of the difference between the commanded position and the actual position of said table, and including means for summing said correction signals with said deflection signals whereby the position of said exposing beam is accurately maintained relative to the actual position of said work piece. 
     
     
       15. The apparatus of claim 14 wherein said measurement unit is an interferometer providing digital actual position signals and where said apparatus includes a digital subtractor means for forming digital error signals as the difference between said digital actual position signals and said digital commands and said apparatus includes digital-to-analog converter means for converting said digital error signals to said correction signals. 
     
     
       16. The apparatus of claim 15 including means for providing a stop scan signal when said error signals exceed predetermined magnitudes and including means for inhibiting further scanning during the presence of said stop scan signals. 
     
     
       17. The apparatus of claim 15 wherein said drive means includes means for providing the drive signals with magnitudes determined by the magnitudes of said error signals. 
     
     
       18. The apparatus of claim 13 wherein said line generator apparatus includes, X and Y beam position counters for storing X and Y axis coordinates, respectively, for providing the X and Y axis coordinate signals of the exposing beam, respectively,   length counter means for storing a length count representing the number of scan locations in a predetermined direction of scan,   control means including scan axis store means for specifying said X axis or said Y axis as said predetermined direction of scan, said control means including clock means for clocking said length counter means to decrement said length counter and for clocking the one of said beam position counters corresponding to said predetermined direction of scan, said control means including direction store means for specifying a positive or negative direction of scan and responsively controlling the incrementing or decrementing, respectively of said one of said beam position counters by said clock means.   
     
     
       19. The apparatus of claim 18 including sequencer means for loading said position counters, said length counter, said scan axis store means and said direction store means in response to line scan information from said processor apparatus. 
     
     
       20. The apparatus of claim 18 including zero detection means, connected to said length counter means, for detecting when said length counter has been decremented to zero to indicate the end of a line scan and including means to reload said counters and said store means in response to said zero detection to commence a new line scan whereby said exposing beam is scanned to expose said pattern a line at a time. 
     
     
       21. The apparatus of claim 13 wherein said processor apparatus is controlled to provide said line scan information as equal length lines starting at the same coordinate whereby rectangular shapes are scanned. 
     
     
       22. The apparatus of claim 13 wherein said processor apparatus is controlled to provide said line scan information as unequal length lines starting at different coordinates whereby special non-rectangular shapes are scanned. 
     
     
       23. A method for controlling an exposing beam to selectively scan a pattern on a work piece comprising, supplying from a computer apparatus digital information records specifying the pattern to be scanned,   converting in a processor apparatus the information records to line scan information,   generating, in a line generator apparatus, beam position signals to scan the exposing beam on the work piece at locations determined by the scan information.   
     
     
       24. The method of claim 23 wherein said converting is performed to provide said line scan information as equal length lines starting at the same coordinate whereby rectangular shapes are scanned.